Design of Large Motion Range and Heavy Duty 2-DOF Spherical Parallel Wrist Mechanism

2013 ◽  
Vol 25 (2) ◽  
pp. 294-305 ◽  
Author(s):  
Koji Ueda ◽  
◽  
Hiroya Yamada ◽  
Hiroaki Ishida ◽  
Shigeo Hirose ◽  
...  
Keyword(s):  
Load Capacity ◽  
Heavy Duty ◽  
Universal Joint ◽  
Compact Structure ◽  
Robotic Arms ◽  
Rescue Robot ◽  
Wide Range ◽  
Spherical Parallel Mechanism ◽  
Motion Range ◽  
Large Motion

Wrist mechanisms are important elements of robotic arms because they significantly affect the arm’s handling ability. Although various wrist mechanisms have been developed to date, a mechanism with a compact structure, a wide range of motion and a large load capacity has not yet been realized. Thus, in this paper, we propose 2-DOF Spherical Parallel (2DSP) mechanism, a heavy-duty wrist mechanism with a large motion range, and clarify its features both analytically and experimentally. The 2DSP mechanism is driven by a 2-DOF spherical parallel mechanism and is supported by a universal joint located at its center. This structure allows the 2DSP mechanism to realize a large motion range and load capacity and simplifies its kinematic analysis. Based on this analysis, we clarify the design process to maximize the motion range and propose a preferable structure of passive joints from the viewpoint of load capacity and production cost. We also describe the detailed design of a 2DSP mechanism for a rescue robot we developed previously and verify the feasibility of the proposed mechanism.

A 6-DOF Compliant Joints-Based Precision Parallel Positioner System Driven by Dual Piezoelectric Actuators

2007 ◽  
Author(s):  
Wei Dong ◽  
Zhijiang Du ◽  
Lining Sun
Keyword(s):  
Parallel Mechanism ◽  
Load Capacity ◽  
Piezoelectric Actuators ◽  
Piezoelectric Ceramics ◽  
Parallel Structure ◽  
Nanometer Scale ◽  
Compliant Joints ◽  
Piezoelectric Motors ◽  
Motion Range ◽  
Large Motion

A precision compliant parallel-structure positioner is presented in this paper, which is dually driven by six piezoelectric motors and six piezoelectric ceramics respectively. This compliant system has a load capacity higher than 2 kg because the parallel mechanism is adopted as the main architecture. This system also can provide larger workspace and higher accuracy simultaneously compared with the conventional compliant positioner systems, because it perfectly integrates two kinds of piezoelectric actuators in one parallel system. The upper platform has the stroke of 10 mm in three linear motion directions and of 6 arc-degrees in three angle motion directions respectively for the adoption of piezoelectric motors as the large motion range actuators. The positioning resolution and repeatability of the upper platform is nanometer scale for the adoption of piezoelectric ceramics as the high precision actuators.

Thermoacoustic Stability Analysis of a Full-Annular Lean Combustor for Heavy-Duty Applications

2021 ◽  
Author(s):  
Daniele Pampaloni ◽  
Antonio Andreini ◽  
Alessandro Marini ◽  
Giovanni Riccio ◽  
Gianni Ceccherini
Keyword(s):  
Stability Analysis ◽  
Gas Turbine ◽  
Flame Temperature ◽  
Numerical Procedure ◽  
Pollutant Emissions ◽  
Computational Time ◽  
Heavy Duty ◽  
Operational Parameters ◽  
3D Fem ◽  
Wide Range

Abstract Thermoacoustic characterization of gas turbine combustion systems is of primary importance for successful development of gas turbine technology, to meet the stringent targets on pollutant emissions. In this context, it becomes more and more necessary to develop reliable tools to be used in the industrial design process. The dynamics of a lean-premixed full-annular combustor for heavy-duty applications has been numerically studied in this work. The well-established CFD-SI method has been used to investigate the flame response varying operational parameters such as the flame temperature (global equivalence ratio) and the fuel split between premixed and pilot fuel injections: such a wide range experimental characterization represents an opportunity to validate the employed numerical methods and to give a deeper insight into the flame dynamics. URANS simulations have been performed, due to their affordable computational costs from the industrial perspective, after validating their accuracy through the comparison against LES results. Furthermore, an approach where the pilot and the premixed flame responses are analyzed separately is proposed, exploiting the independence of their evolution. The calculated FTFs have been implemented in a 3D FEM model of the chamber, in order to perform linear stability analysis and to validate the numerical approach. A boundary condition for rotational periodicity based on Bloch-Wave theory has been implemented into the Helmholtz solver and validated against full-annular chamber simulations, allowing a significant reduction in computational time. The reliability of the numerical procedure has been assessed through the comparison against full-annular experimental results.

Stability-Optimized Clearance Configuration of Fluid-Film Bearings

2006 ◽  
Vol 129 (1) ◽  
pp. 106-111 ◽  
Author(s):  
Koichi Matsuda ◽  
Shinya Kijimoto ◽  
Yoichi Kanemitsu
Keyword(s):  
Fourier Series ◽  
Load Capacity ◽  
Fluid Film ◽  
Eccentricity Ratio ◽  
Rotating Speed ◽  
Fluid Film Bearings ◽  
Wide Range ◽  
Jeffcott Rotor ◽  
The Stability ◽  
Frequency Ratios

The whirl instability occurs at higher rotating speeds for a full circular fluid-film journal bearing, and many types of clearance configuration have been proposed to solve this instability problem. A clearance configuration of fluid-film journal bearings is optimized in a sense of enhancing the stability of the full circular bearing at high rotational speeds. A performance index is chosen as the sum of the squared whirl-frequency ratios over a wide range of eccentricity ratios, and a Fourier series is used to represent an arbitrary clearance configuration of fluid-film bearings. An optimization problem is then formulated to find the Fourier coefficients to minimize the index. The designed bearing has a clearance configuration similar to that of an offset two-lobe bearing for smaller length-to-diameter ratios. It is shown that the designed bearing cannot destabilize the Jeffcott rotor at any high rotating speed for a wide range of eccentricity ratio. The load capacity of the designed bearings is nearly in the same magnitude as that of the full circular bearing for smaller length-to-diameter ratios. The whirl-frequency ratios of the designed bearing are very sensitive to truncating higher terms of the Fourier series for some eccentricity ratio. The designed bearings successfully enhance the stability of a full circular bearing and are free from the whirl instability.

scholarly journals A New 4500-HP Gas Turbine for Pipeline Industrial Service

1970 ◽  
Author(s):  
R. R. Oliver ◽  
F. Fraschetti
Keyword(s):  
Gas Turbine ◽  
Mechanical Design ◽  
Maximum Efficiency ◽  
Heavy Duty ◽  
Cooperative Effort ◽  
Package Design ◽  
Wide Range ◽  
Industrial Service ◽  
Design Options ◽  
Regenerative Cycle

This paper describes the performance and mechanical design of a 4500-hp, two shaft heavy duty simple or regenerative cycle gas turbine. This machine resulted from an international cooperative effort of the joint authors’ respective companies. Initially planned for gas pipelines and process applications, a line of load compressors has been integrated into the single package design. Options include indoor or outdoor models and geared or direct mechanical output for applications not served by the integral compressor models. A variable area load turbine nozzle assures maximum efficiency over a wide range of load, speed, and amibient conditions.

20 Years Experience Burning Heavy Fuels in Heavy Duty Gas Turbines

1973 ◽  
Author(s):  
A. O. White
Keyword(s):  
Gas Turbines ◽  
Processing System ◽  
Operating Experience ◽  
Field Tests ◽  
Early Experience ◽  
Liquid Fuels ◽  
Heavy Duty ◽  
Fuel Processing ◽  
Wide Range ◽  
Heavy Fuels

This paper covers the early experience of the author’s company in burning residual oils in their gas turbines and the problems that occurred. The laboratory invesgations and field tests that resulted in a fuel processing system that permitted satisfactory operation on a wide range of liquid fuels are described. The operating experiences, where residual fuels were successfully burned in a large number of units, are described. The most recent operating experience with residual and crude oils and heavy distillates is also covered. A list of the various installations with dates and hours of operation is included and it is concluded that heavy duty gas turbines burning heavy fuels will be established as the up-to-date source of economical power in many applications.

Theory Versus Experiment for the Effects of Pressure Ratio on the Performance of an Orifice-Compensated Hybrid Bearing

1998 ◽  
Vol 120 (4) ◽  
pp. 930-936 ◽  
Author(s):  
P. Mosher ◽  
D. W. Childs
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Load Capacity ◽  
Dynamic Stiffness ◽  
Pressure Ratio ◽  
Navier Stokes ◽  
Rotordynamic Coefficients ◽  
Wide Range ◽  
Bearing Load ◽  
Hybrid Bearing

This research investigates the effect of varying the concentric recess pressure ratio of hybrid (combination hydrostatic and hydrodynamic) bearings to be used in high-speed, high-pressure applications. Bearing flowrate, load capacity, torque, rotordynamic coefficients, and whirl frequency ratio are examined to determine the concentric, recess-pressure ratio which yields optimum bearing load capacity and dynamic stiffness. An analytical model, using two-dimensional bulk-flow Navier-Stokes equations and anchored by experimental test results, is used to examine bearing performance over a wide range of concentric recess pressure ratios. Typically, a concentric recess pressure ratio of 0.50 is used to obtain maximum bearing load capacity. This analysis reveals that theoretical optimum bearing performance occurs for a pressure ratio near 0.40, while experimental results indicate the optimum value to he somewhat higher than 0.45. This research demonstrates the ability to analytically investigate hybrid bearings and shows the need for more hybrid-bearing experimental data.

Combustion Instabilities Damping System Development for Dry Low NOx Emissions Operability Enhancement of a Heavy-Duty Gas Turbine

2019 ◽  
Author(s):  
Matteo Cerutti ◽  
Nicola Giannini ◽  
Bruno Schuermans ◽  
Riccardo Brenci ◽  
Alessandro Marini ◽  
...  
Keyword(s):  
Growth Rate ◽  
Gas Turbine ◽  
Growth Rates ◽  
Fine Tuning ◽  
Optimized Design ◽  
Nox Emissions ◽  
Preliminary Design ◽  
Heavy Duty ◽  
Wide Range ◽  
Heavy Duty Gas Turbine

Abstract This paper describes the development phases of a damping system for combustion instability reduction in an annular type combustor for heavy-duty gas turbine applications. As reported by the authors in a previous paper, the full scale annular test rig allowed for an extensive characterization of the combustor with realistic acoustic boundaries at engine-relevant conditions. Emissions and operability assessment over a wide range of load conditions was performed, allowing the evaluation of the response of the system near the thermo-acoustic instability onset. The instability is quantified by its acoustic growth rate. This quantity is a crucial input in the design process of dampers. A methodology has been used to extract these growth rates form measured pulsation data. Experimentally determined growth rates have been evaluated for different fuel flow rate split between the main and the pilot injections, providing input to dampers preliminary design. Given current combustor architecture constraints, a first attempt configuration has been proposed and performances evaluated in the full annular rig. Dampers have been equipped with dynamic sensors and thermocouples with the purpose of measuring the growth rate abatement and the consequent NOx emissions reduction. A dedicated numerical toolbox, in-house developed by GE Power, has been used for both dampers preliminary design and growth rate reduction evaluation. Fine tuning of dampers elements as well as design assumptions adjustments required additional experimental evaluations and design iterations. Encouraged by the successful test in the concept phase, an optimized design for engine implementation was defined, that featured a significant increased damper volume, involving combustor parts re-design. The optimized configuration was finally tested in full annular rig and results demonstrated an important enhancement of operability while maintaining NOx emissions below the target levels.

Characterization of Lobula Giant Neurons Responsive to Visual Stimuli That Elicit Escape Behaviors in the Crab Chasmagnathus

2007 ◽  
Vol 98 (4) ◽  
pp. 2414-2428 ◽  
Author(s):  
Violeta Medan ◽  
Damián Oliva ◽  
Daniel Tomsic
Keyword(s):  
Visual Memory ◽  
Visual Stimuli ◽  
Visually Guided ◽  
Wide Range ◽  
Large Motion ◽  
Escape Behaviors ◽  
Neuronal Type

In the grapsid crab Chasmagnathus, a visual danger stimulus elicits a strong escape response that diminishes rapidly on stimulus repetition. This behavioral modification can persist for several days as a result of the formation of an associative memory. We have previously shown that a generic group of large motion-sensitive neurons from the lobula of the crab respond to visual stimuli and accurately reflect the escape performance. Additional evidence indicates that these neurons play a key role in visual memory and in the decision to initiate an escape. Although early studies recognized that the group of lobula giant (LG) neurons consisted of different classes of motion-sensitive cells, a distinction between these classes has been lacking. Here, we recorded in vivo the responses of individual LG neurons to a wide range of visual stimuli presented in different segments of the animal's visual field. Physiological characterizations were followed by intracellular dye injections, which permitted comparison of the functional and morphological features of each cell. All LG neurons consisted of large tangential arborizations in the lobula with axons projecting toward the midbrain. Functionally, these cells proved to be more sensitive to single objects than to flow field motion. Despite these commonalities, clear differences in morphology and physiology allowed us to identify four distinct classes of LG neurons. These results will permit analysis of the role of each neuronal type for visually guided behaviors and will allow us to address specific questions on the neuronal plasticity of LGs that underlie the well-recognized memory model of the crab.

Foil Bearings Makes Oil-Free Turbocharger Possible

2005 ◽  
Author(s):  
Crystal A. Heshmat ◽  
Hooshang Heshmat ◽  
Mark J. Valco ◽  
Kevin C. Radil ◽  
Christopher Della Corte
Keyword(s):  
High Speed ◽  
Solid Lubricant ◽  
Load Capacity ◽  
Maximum Load ◽  
Solid Lubricant Coating ◽  
Foil Bearings ◽  
Wide Range ◽  
Rotor Bearing ◽  
Component Development ◽  
Bearing System

This paper describes an oil-free, 150 Hp turbocharger that was successfully operated with compliant foil bearings in a range of pitch and roll angles, including vertical operation, thereby demonstrating its viability for aircraft applications. On a gas test stand the turbocharger was operated to 120,000 rpm, under extreme conditions. In addition, the compliant foil bearing-supported turbocharger successfully tolerated shock and vibration of 40 g. Advanced technologies have been applied to the second generation of this turbocharger, shown in Figure 1, including self acting, compliant foil hydrodynamic air bearings with advanced coatings capable, of operation above 815 °C (1500°F). Journal foil bearings with maximum load capacity up to 670 kPa (97 psi) were used in conjunction with thrust foil bearings capable of maximum loads to 570 kPa (83 psi). Bearing component development tests demonstrated 30,000 start stop cycles at 815 °C (1500°F) with a newly developed, solid lubricant coating, KOROLON™. KOROLON™ exhibits a coefficient of friction of less than 0.1 at a wide range of temperatures. Current-designed foil bearings with KOROLON™ have immensely decreased turbolag, allowing acceleration from rest to over 100,000 rpm in less than 2 seconds. Advanced bearing stiffness maintained rotor total axial end-to-end motion within 100 microns (0.004 inch). Total radial static and dynamic motion was controlled within 25 microns (0.001 inch). Development of this high speed turbomachine included bearing and solid lubricant component development tests, rotor-bearing dynamic simulator qualification and gas stand tests of the assembled turbocharger. Gas stand and simulator test results revealed stable bearing temperatures, low rotor vibrations, good shock tolerance and the ability of the rotor bearing system to sustain overspeed conditions beyond 120,000 rpm. This combination of component and integrated rotor-bearing system technology addresses many of the issues associated with application of compliant foil bearings to industrial compressors, blowers, and gas turbine engines, overcoming many of the inherently show-stopping and debilitating features of rolling element bearings, i.e., speed and temperature limitations.

Analysis of annulus-shaped compliant pivot with series–parallel leaves

2012 ◽  
Vol 227 (5) ◽  
pp. 1090-1101 ◽  
Author(s):  
Shusheng Bi ◽  
Tao Qiao ◽  
Hongzhe Zhao ◽  
Yanbin Yao
Keyword(s):  
Accurate Approximation ◽  
Analysis Software ◽  
Element Analysis ◽  
Motion Range ◽  
Stress Prediction ◽  
Large Motion ◽  
Displacement Behavior ◽  
Load Displacement ◽  
Geometric Compatibility ◽  
Detailed Work

Annulus-shaped compliant pivot, formed by well-proportioned compliant modules between the outer ring and inner ring, can be employed in precision mechanical systems due to good performances. Especially for the multi-series leaves in one module, the annulus-shaped compliant pivot can fulfill a large displacement range without any axial drift in theory. In the design of the annulus-shaped compliant pivot, the load–displacement behavior and the stress analysis with analytical forms are important consideration. However, in the literature, there is few detailed work. In this article, a general annulus-shaped compliant pivot model formed by series–parallel leaves is first analytically established for the load–displacement behavior and the stress prediction. These calculations are based on accurate approximation of a beam flexure. Firstly, a loaded moment is decomposed into universal loads by combining the geometric compatibility condition. The stiffness accurate approximation is then analytically obtained, which provides a simple design strategy. Furthermore, the stresses in every leaf are obtained so that the annulus-shaped compliant pivot with large motion range can be actualized by stress checking. Lastly, the analytical model has been verified by commercial finite element analysis software ANSYS.

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